Need some new front tyres and going through the whole selection dilemma. Just wondering how much difference the "fuel efficiency" rating of a tyre actually makes in real terms...? Is there going to be a noticeable difference between, for example, an A and an E? Or do you not take too much notice of this?

I take no notice what so ever as i want the best performing tyre for grip, ie traction / braking / cornering in the conditions the tyre will be used.

The same with the Noise Rating.

Sadly the 'Stickers / codes' for that on the tyres are not always to be paid that much attention to either, but then they do give some indication as to what the testing results showed.

Fuel efficiency can be achieved by tyre pressures, and modifying driving behaviour, but safety in the wet & cold or even the warm & dry should not be compromised IMO to get better MPG even when driving safely for the conditions because tyres are 'Eco'.

Edited 7 December, 20169 yr by Offski

Just found this on BlackCircles:

 

A tyre's rolling resistance score ranges from A to G. Over the life of the tyre, fitting an A rated tyre could save you up to 6 litres of fuel when compared to a G rated tyre.

 

"Could" save 6 litres over the lifetime of a tyre?? Not exactly disastrous! 

Well I recently changed my wheels as the car had stupid 19" wheels on and the tyres were E and F rated for fuel efficiency (Arrowspeed and Kenda- awful things!).

 

I bought a set of Pirelli P7 Cinturato Blues and the difference has been huge. They are AA rated for wet grip and fuel efficiency.

 

Previously I could not get over 500 miles from a tank no matter what I did. Even on a long drive where I should have been getting 50+mpg we were struggling to do 40. Long drive to Germany and back and the 58 litre tank was empty after around 480miles!

 

Now though on a long run it's easy to get 600+ miles out of a tank and the trip computer average has gone from 37.8 to 43.5mpg with mainly short/town trips and the odd A road drive. The MPG round town is pretty much the same and doing exclusively short runs will only see about 450-480 miles from a tank as it's the torque converter and stop-start that matter here not the tyres.

 

The old tyres were VERY noisy to the point where I was about to get the car booked into a garage to check for failed wheel bearings. So I think the tyres were dreadful then going to a brand new A rated tyre. I also had very bad wheel wobble which was either the wheels, tyres or both. I think even buying some new decent tyres of any rating would have improved the economy.

 

So yes they can make a big difference but depends what tyres you have at the moment.

Edited 7 December, 20169 yr by Phil-E

The important thing to note about tyre rating data is that it's all manufacturer self-certification.

 

I mostly believe Phil's account, but ISTR that he changed wheel diameter at the same time? That also has an effect on fuel economy (and more than you'd expect because the momentum of a rolling wheel rises with increased mass and as the 4th repeat 4th power of road speed so an apparently small reduction in wheel mass has a disproportionate effect on economy).

The old tyres were VERY noisy to the point where I was about to get the car booked into a garage to check for failed wheel bearings. 

 

This is exactly what I've just experienced...thought a wheel bearing was on the way out but the garage checked it and said the bearings were fine and it was the tyres that were the problem.

 

Will you be keeping the Cinturato Blues on over winter? I believe they're rated as summer tyre, but I'm not sure I've got the finances (or inclination!) to have two sets of tyres so I'm looking for a good year-round option.

They are just rated as a summer tyre yes. I did look at all season tyres but the choices were slim and the prices higher. We're not dependent on our car, work from home, live in a flat city (no hills) and can walk if the weather is bad.

 

If I do get winter tyres again I will do as I did with the Octavia and have a set of extra wheels with dedicated winter tyres rather than all seasons.

 

They are very grippy though and inspire confidence in both the dry and wet. I also floored it in the frosty conditions the other day too (light frost on the road) and barely a hint of any slip. For an "eco" tyre I am very impressed. Very quiet, MPG good and yet if the car is pushed it feels very planted and I can floor it off the line without any drama and given that I have 400nm of torque and a torque converter (amplification of torque) the grip off the line is impressive!

 

They are XL rated too btw which stiffens up the sidewalls when lugging a heavy 1,700kg convertible around!

 

The important thing to note about tyre rating data is that it's all manufacturer self-certification.

 

I mostly believe Phil's account, but ISTR that he changed wheel diameter at the same time? That also has an effect on fuel economy (and more than you'd expect because the momentum of a rolling wheel rises with increased mass and as the 4th repeat 4th power of road speed so an apparently small reduction in wheel mass has a disproportionate effect on economy).

 

It was a very small reduction as although I went from 19" to 17" I went up from 35 to 45 profile tyres so overall reduction in diameter of 0.8%. Or rather the 19" wheels had been an increase of 0.8% and I've gone back to standard. So yes that will likely have had an affect on the economy although how much 0.8% difference makes I'm not sure.

It was a very small reduction as although I went from 19" to 17" I went up from 35 to 45 profile tyres so overall reduction in diameter of 0.8%. Or rather the 19" wheels had been an increase of 0.8% and I've gone back to standard. So yes that will likely have had an affect on the economy although how much 0.8% difference makes I'm not sure.

Did you weigh the wheel/tyre combo before and after? I'm talking about mass, not rolling radius (but I agree the change in RR won't make much difference either way).

Ah yes. That's a point. Didn't think of the weight difference. There must be a difference as it's 19" vs 17" so less metal to start and the old ones had more spokes than the new.

 

19"

 

17"

Ah yes. That's a point. Didn't think of the weight difference. There must be a difference as it's 19" vs 17" so less metal to start and the old ones had more spokes than the new.

 

The difference will be surprising. I weighed my old 6x13" capri alloy vs the new 8x15" wheels using the time honoured 'arm scales' and it feels well over double the weight! 15" feel around 15kg, whereas the 13" feel around 3-5kg (Inc tyres).

The difference will be surprising. I weighed my old 6x13" capri alloy vs the new 8x15" wheels using the time honoured 'arm scales' and it feels well over double the weight! 15" feel around 15kg, whereas the 13" feel around 3-5kg (Inc tyres).

I'd be surprised if the 6x13 is that light (even if it's the RS 4 spoke).

It was a very small reduction as although I went from 19" to 17" I went up from 35 to 45 profile tyres so overall reduction in diameter of 0.8%. Or rather the 19" wheels had been an increase of 0.8% and I've gone back to standard. So yes that will likely have had an affect on the economy although how much 0.8% difference makes I'm not sure.

 

That's quite a drop in size Phil so the weight reduction will definitely play a part in the fuel economy figures.  When I had the Vectra (same family tree as the Saab I think?) it was running the OEM Ronal Vauxhall wheels.  They weighed in at 24.5kg each, including the tyre.  I'm assuming that the Saab wheels are of a similar weight and you were running 235 35 19"?  I recently sold some 18" Zenith wheels and on the same scales they came in at 23.5kg including the tyre.  I have just bought some 17" TD Pro Race 1.2 and they are 17.8kg each including the tyre.  

When I kept the 19" wheel size on the Vectra I bought some TD Imolas and they were nearer 22kg each with the same 235 35 19" tyres.  I noticed that the car accelerated quicker and that it handled better in the corners.  Fuel consumption was still shocking though.

It'd be interesting - from my geeky viewpoint anyway - to know how much the 17" Saab wheels weigh as I looked at a set of those for winter wheels for the Vectra.  

Skinnyman's figures are the sort of weight drop I was expecting. I'm not going to work it out "properly", just do mass^4, but those give the 19" as 234,256 units, the 17" as 83,521 so the 17" are 35.65% the rolling mass of the 19". You see why the smaller wheels make the car faster and more economical now?

Next time I have a wheel off I'll pop it on some scaled and get an idea vs the 19".

 

Yes the tyres were 235/35/19 though with a tiny bit of stretch as those wheels (when fitted to the 9-5) should have 245/35/19.

 

And yes... my Saab 9-3 shares it's platform with the Vectra and also the Cadillac BLS... with a Fiat/Alfa/GM made engine.